CVE-2015-2059 in libin
Summary
by MITRE
The stringprep_utf8_to_ucs4 function in libin before 1.31, as used in jabberd2, allows context-dependent attackers to read system memory and possibly have other unspecified impact via invalid UTF-8 characters in a string, which triggers an out-of-bounds read.
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Analysis
by VulDB Data Team • 06/09/2022
The vulnerability identified as CVE-2015-2059 represents a critical memory safety issue within the libin library version 1.30 and earlier, which is utilized by the jabberd2 messaging server. This flaw manifests in the stringprep_utf8_to_ucs4 function that processes UTF-8 character sequences for string preparation operations. The vulnerability stems from inadequate input validation mechanisms that fail to properly handle malformed UTF-8 sequences, creating a scenario where attackers can manipulate string inputs to trigger unintended memory access patterns. The issue is classified as context-dependent because the attack requires specific conditions to be met, including the ability to inject malformed UTF-8 data into the target system. This vulnerability operates at the intersection of character encoding processing and memory management, making it particularly dangerous in networked applications that process user-provided data.
The technical exploitation of this vulnerability occurs through a buffer overflow condition that results in an out-of-bounds read operation. When the stringprep_utf8_to_ucs4 function encounters invalid UTF-8 characters, it fails to properly validate the input sequence boundaries, leading to memory access beyond the allocated buffer limits. This memory corruption can result in information disclosure, where sensitive data from adjacent memory locations becomes accessible to the attacker. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software implementations, and represents a classic example of how improper input validation can lead to memory safety issues. The flaw specifically impacts the UTF-8 to UCS-4 conversion process, where the function attempts to map variable-length UTF-8 sequences to fixed-length UCS-4 code points without proper boundary checking.
The operational impact of CVE-2015-2059 extends beyond simple information disclosure to potentially enable more sophisticated attacks within the jabberd2 ecosystem. Since jabberd2 serves as an instant messaging server that processes messages from multiple users, an attacker could exploit this vulnerability to gain access to sensitive session data, user credentials, or system memory contents. The vulnerability's presence in a messaging server creates a particularly concerning threat model because it could be leveraged to compromise user communications, potentially leading to account takeovers or unauthorized access to private conversations. The unspecified additional impacts mentioned in the description suggest that the memory corruption could potentially enable code execution or other advanced attack vectors depending on the specific memory layout and system configuration.
Mitigation strategies for this vulnerability require immediate patching of the libin library to version 1.31 or later, where the input validation has been strengthened to properly handle malformed UTF-8 sequences. System administrators should also implement input sanitization measures at the application level, particularly for any string processing functions that handle user-provided data. The fix addresses the underlying issue by implementing proper boundary checking and validation of UTF-8 character sequences before attempting conversion operations. Organizations should also consider implementing network-level protections such as input filtering and monitoring for malformed UTF-8 sequences in communication protocols. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and information gathering through memory corruption, with potential for lateral movement if the compromised server has access to additional network resources. The vulnerability demonstrates the importance of proper input validation in cryptographic and encoding libraries, as these components often serve as attack surfaces for more complex exploitation chains.